In recent years, a semiconductor device has been developed and used as a CPU and a memory. Among them, a semiconductor device which consumes large power has a problem that a larger battery and a cooling fan are required, thereby the electronic apparatus itself is increased in size. In view of the foregoing, a composite semiconductor device is suggested, which has a structure where a wiring substrate and a package are attached to each other so as to satisfy high thermal conductivity and low elasticity.
[Patent Document 1]
Japanese Patent Laid-Open No. 07-74282
A semiconductor device capable of transmitting and receiving data has been developed, which is called a wireless tag, an RFID tag, or the like. The semiconductor device which has been put to practical use comprises an antenna and a circuit formed using a semiconductor substrate (an IC chip) in many cases. The IC chip comprises a plurality of transistors each of which has a fixed threshold voltage.